3T-Y winding connection for three phase multiple-speed motor

Abstract

A three-phase, multi-speed electric induction motor assembly is configured to include a controller to change motor speeds. The motor assembly includes a stator core assembly, a pair of main winding coil groups corresponding with each phase, and a pair of selectable extra winding coil groups corresponding with each phase. During the lower-speed operation, the controller connects a first set of three leads to a power source such that only the main coil groups are energized. During the higher-speed operation, the controller connects a second set of three leads to the power source such that both the main coil groups and the selectable extra coil groups are energized.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application claims the benefit of and priority from Chinese Patent Application No. 201010204549.4, filed Jun. 18, 2010, the entire disclosure of which is hereby incorporated by reference herein.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to a three-phase, multi-speed electric induction motor assembly. More specifically, the present invention concerns a three-phase, multi-speed electric induction motor assembly that includes selectable extra winding coil groups that are energized only during a selected speed operating mode to improve balanced motor efficiency between multiple speed operating modes.[0004]2. Discussion of the Prior Art[0005]Those of ordinary skill in the art will appreciate that three-phase electric induction motors are known to be generally effective and are commonly used in a variety of industrial applications. Furthermore, three-phase electric inductio...

AI Technical Summary

Benefits of technology

[0010]According to an aspect of the present invention, an inventive 3T-Y winding connection form has been developed for use in a three-phase, multi-speed electric induction motor. The new 3T-Y winding connection form includes a special winding distribution to improve lower-speed efficiency over the known prior art connection form options. Furthermore, the new 3T-Y winding connection form includes a unique selectable extra winding coil group that corresponds with each main winding coil group for each phase to improve higher-speed efficiency over the known prior art connection form options. Thus, the new 3T-Y winding connection form effectively balances multiple speed efficiencies in a manner unrealized by prior art winding connections.

[0011]The unique selectable extra winding coil groups are preferably energized only during higher-speed operation and serve to balance high-speed and low-speed breakdown torque, depending on design requirements, and to increase the number of high-speed effective turns. In one embodiment, a three-phase, multi-speed electric induction motor including the new 3T-Y winding connection form achieved an efficiency of at least about 84% during lower-speed mode operation and an efficiency of at least about 88% during higher-speed mode operation. These efficiency improvements are realized while slightly reducing the slot fill percentage relative to prior art connections, and while using approximately equal weights of winding material (e.g., copper wire). Thus, the benefits of the new 3T-Y winding connection form may be obtained without significantly adding to production costs.

Problems solved by technology

While the YY-Δ and the YY-Y winding connection forms have been satisfactory in some respects, both connection forms present difficulty in balancing both low-speed efficiency and high-speed efficiency, leading to drawbacks in operating costs.

Such difficulty in balancing efficiency in both the low-speed mode and the high-speed mode may be particularly detrimental when trying to drive a light load at a very high efficiency.

In the YY-Δ winding connection form, the high-speed mode is often too weak, and the low-speed mode is often too strong.

Such a connection form thus makes the low-speed operation have a tendency to become very saturated at a light load, leading to a generally lower efficiency during the low-speed mode.

In the YY-Y winding connection form, the high-speed mode is often too strong, and the low-speed mode is often too weak.

Such a connection form thus makes the high-speed operation have a tendency to become very saturated at a light load, leading to a generally lower efficiency during the high-speed mode.

Even with such a choice, it remains undesirable to suffer a lower efficiency during one of the speed modes, especially when trying to drive a light load at a very high efficiency.

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